In order to quantify the mass and concentration of a sensing target which is included in a very small amount in an environment or in a living body such as, for instance, an environmental pollutant like dioxin, PCB (polychlorinated biphenyl), and the like, contained in a river, various antibiotics used for raising fishes and are remained in the blood of the raised fishes, and diseased substances such as prion which causes BSE (bovine spongiform encephalopathy) in an animal body tissue, there is known a sensing device using a crystal sensor being a sensing sensor provided with a crystal vibrator having, for instance, a crystal piece as a piezoelectric piece, in which an excitation electrode for exciting the crystal piece is respectively provided to one surface side and the other surface side of the crystal piece.
If explained more in detail regarding this sensing device, the sensing device includes, other than the above-described crystal sensor, for example, a frequency measuring device being electrically connected to the crystal sensor and having a frequency detecting section for detecting a frequency generated by the crystal piece, and a PC (personal computer) being electrically connected to the frequency measuring device and having a monitor, or the like, as an output section, for example. Further, at one surface side of the crystal vibrator, an absorbing layer having, for instance, an antibody adhered to the surface thereof is provided, in which the antibody is designed to selectively absorb one of the sensing target such as mentioned above, for example, by an antigen-antibody reaction, and when the sensing target is absorbed in the absorbing layer, the frequency of the crystal piece varies in accordance with the absorption amount of the sensing target. In the above-described PC, a software which analyzes the frequency variation detected by the frequency detecting section of the frequency measuring device and graphically displays the frequency variation on the monitor, for example, is installed.
With the use of thus structured sensing device, when, for example, a user drops a sample solution containing the sensing target on the crystal vibrator after dropping a solvent, the sensing target is absorbed in the absorbing layer, an oscillation frequency of the crystal vibrator decreases in accordance with the absorption amount, and the frequency variation is graphically displayed on the monitor. The user can determine the mass and concentration of the sensing target included in the sample solution by reading the frequency variation amount from the graph and by performing a predetermined calculation based on the variation amount.
Meanwhile, in order to secure the safety of the human body, in an environmental field, there is a case in which a sample solution is prepared by, for example, adding a solvent under a predetermined atmosphere to water collected as a specimen, or by making the air collected as a specimen dissolved in a solvent, and by comparing concentrations of the respective environmental contaminants such as, for instance, the aforementioned dioxin and PCB included in the sample solution, with standard concentrations (tolerance amount) being previously set for each of the various environmental contaminants, for example, to thereby determine the largeness or smallness of these concentrations. Further, also in a food sanitation field, there is a case in which a sample solution is prepared by a specimen such as, for example, the blood of an animal, and by comparing a concentration of a substance toxic to the human body such as various antibiotics included in the sample solution with a standard concentration being previously set for each of the toxic substances, for instance, to thereby determine the largeness or smallness of these concentrations. The aforementioned conventional sensing device can also be applied for performing such determinations, but, in such a case, the user has to perform, other than the aforementioned quantification using the sensing device, an examination and a storage of a standard concentration of the quantified substance, and thereafter, the user compares the standard concentration with the quantified value obtained by the sensing device by matching them with each other, to thereby determine the largeness or smallness of the concentrations, which becomes a great burden on the user when performing determinations with respect to a plurality of sensing targets, for instance.
Note that although a sensing device provided with a crystal sensor is described in Patent Document 1, an aim thereof is to enhance the sensitivity by connecting various components included in the device without using any cables, so that the above-described problems cannot be solved with it.
Patent Document 1
Japanese Patent Application Laid-open No. 2001-083154 (Paragraph 0007, FIG. 1)